ROI of window film: short if you take it off in the winter to gain heating --
some of my Gila film has been in place for 4y now.
2 y/a I removed film from patio door for plants -- did not do that last yr -- PIA to clean adhesive off glass -- not bad = ~1.5h, PIA to install new & $30 of film --
I have film on seven 3x5ft combination storm windows, one 3x3ft window, one 2'8 storm door, one 6ft patio door which has dbl pane glass -- Yeh, Gila states not to install on storms, nor over dbl pane, but I was not about to cut small pieces of film to fit the upper wood window sashes with 6 lites ~10*12" ea.
BTW, my 1974 wood windows are well weatherstripped! channels are alum with plas inserts -- plas is crumbling, but seals still work -- at least the builder did not cheat there -- [ could not hang doors plumb! ]
harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!
I have put the Gila film on my sons bedroom south facing windows and it definitely helps reduce the heat gain in his room in the summer. It's not a miracle, but it does increase comfort and reduce some load on the AC in there. For that sort of thing I think it's an excellent choice.
I started preparing to do it all around a big sun porch like room here (used to be an indoor swimming pool, previous owners filled that in and put down nice tile it's the family room now) but I have decided to go with removable solar screen on the outside so that i can remove them in the winter time. I'll get to building those as soon as I figure out where I'll store them in the winter time...